1. Field of the Invention
This invention relates to manufacturing methods and more particularly to methods of manufacturing coil cores with flange-embedded connecting pins.
2. Prior Art
Coil bodies or cores are frequently formed by injection-molding and include central core bodies or winding tubes having axially spaced-apart radially projecting flanges with connection pins embedded in one of the flanges.
Typically, many coil designs, such as for electromagnetic relays and the like, require coil bodies or cores which are specifically designed to provide the greatest possible area for the coil winding while maintaining an overall objective of providing the smallest possible complete coil. In order to achieve such constructions, the coil core must be formed having flanges which have axially thin walls. However, since the flange walls generally have to receive and hold connecting pins to be connected to the ends of the winding, the thin walls present a problem in that it becomes extremely difficult to provide a dimensionally stable flange-pin lock firmly holding the connecting pin in the flange. It is well known that in order to provide a sufficiently stable mechanical lock on a straight piece of wire embedded in an injection molded part, the portion of the wire encased in the injected material must have a certain mimimum length. When the thin material of the flange is such as to prevent this minimum length from being established, the connecting pin must be deformed over a portion of its axial length which is embedded in the flange.
Such deformation of the wire connection pins in injected-molded cores has been used. One method of manufacturing such devices involves the crushing of the wire in the injection mold either through a joggling of the wire by means of movable slide mold members or through the provision of additional, extraneous, bending devices. Such prior art methods involve, on the one hand, an additional bending stage, and on the other hand, an inability to predict the direction the deformation of the wire will undergo. Further, in order for any degree of success to occur, the prior art methods can only be used where the total volume of plastic in the area of the connection pin is such as to guarantee that an adequate mass of injected material will be present on each side of the embedded wire. Thus, such methods are not usable whenever the connecting pin is to be fixed at any spot on the coil flange which is defined by close tolerances and where it cannot be guaranteed that a large plastic mass will be present, such as closely adjacent the peripheral edge of the flange.
It would therefore be an advance in the art to provide a method of embedding connecting pins in thin flange coil cores which increase the reliability of the embedding of the pin while at the same time allowing usage of thin flanges.